This project deals with the immunobiology of HLA and its clinical applications. Studies will focus on three areas. One is to identify and characterize B cell specific alloantisera, to detect DRw markers and antigens controlled by linked genes, and to characterize the role of such antigens in lymphocyte activation in the mixed leukocyte culture and in the secondary allogeneic response. We also will search for HLA-D homozygous typing cells with new specificities and determine the relationship between HLA-D and DR determinants. Studies of HLA and disease associations will concentrate on the complications of juvenile diabetes melitius, thyroid neoplasia, acute lymphocytic leukemia, and ocular histoplasmosis.